Acquired inhibitor of coagulation factor V is a rare clinical condition and may cause significant morbidity and mortality. We report here the first Korean case of acquired isolated factor V inhibitor developed in a 73-year-old male patient after surgery for pancreatic head carcinoma. At post-operation day 2, intra-abdominal bleeding was recognized that was associated with a prolonged prothrombin time and activated partial thromboplastin time. The prolongation of both conditions was not corrected by a mixing test and factor V activity was reported to be 2%. Quantified titers of inhibitors were increased from 3.5 Bethesda unit to 8.4 Bethesda unit during follow-up analysis. In spite of the treatment with steroids and intravenous immunoglobulins, the case ended fatally. When acquired bleeding tendency with prolonged coagulation screening test is observed, evaluation of inhibitors of coagulation factors may be essential for the diagnosis and following appropriate management of the condition. (Korean J Hematol 2008; 43:190-193.)

Keywords: Factor V, Blood coagulation factor, Inhibitor